Electrochemical Oxidation of Carbon Monoxide on Unsupported Gold Nanospheres in Alkaline Medium
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ORIGINAL RESEARCH
Electrochemical Oxidation of Carbon Monoxide on Unsupported Gold Nanospheres in Alkaline Medium Nolwenn Mayet 1 & Karine Servat 1 & K. Boniface Kokoh 1
&
Teko W. Napporn 1
Accepted: 5 October 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Carbon monoxide (CO) is intensively studied as a model molecule for organics oxidation reaction or as a strong adsorbate on noble metal surfaces. In this work, quasispherical gold nanoparticles (AuNPs) prepared by a revisited Turkevich method were electrochemically characterized. Physical and electrochemical measurements demonstrated the presence of (111) and (110) facets. These unsupported NPs were used to study the effect of the upper potential limit and gold oxide formation on CO oxidation in alkaline medium. The results demonstrate that hydroxide species are crucial to oxidize CO, whereas the gold oxides species do not play a critical role. Keywords Carbon monoxide . Electrocatalysis . Gold nanoparticles . Cyclic voltammetry . Underpotential deposition
Introduction The electrochemical oxidation of organic molecules leads often to the formation of carbon monoxide which is considered as a poisoning species for various noble metal electrodes like platinum [1]. Therefore, the oxidation of carbon monoxide (CO) becomes one of the most investigated reactions in electrocatalysis in the aim of finding the efficient way for overcoming the electrode deactivation due to its strong adsorption. On Pt electrode, CO electrooxidation is extensively studied both in acid and alkaline media for understanding the reaction mechanism and to fabricate tolerant and active electrode materials [2]. For this purpose, the use of disseminated noble metal nanoparticles on high specific surface area materials as the carbon substrate is a way to avoid strong adsorption of CO and promote its oxidation. Conversely to platinum which strongly interacts with CO, bulk gold is considered as the most stable and less active metal [3]. Therefore, under standard conditions, the poisoning effect by CO usually evidenced electrochemically on Pt by CO stripping is not * K. Boniface Kokoh [email protected] * Teko W. Napporn [email protected] 1
Université de Poitiers, IC2MP, UMR-CNRS 7285, 4 rue Michel Brunet, B27, TSA 51106, 86073, Poitiers Cedex 09, France
commonly experienced on Au. Indeed, the electrochemical interaction between the surface of bulk gold electrode and CO was earlier studied in 1960s by Roberts et al. [4] in acid and alkaline media. The important role of hydroxides in the oxidation process was pointed out. In heterogeneous catalysis, the oxidation of CO is widely studied on supported gold nanoparticles. Indeed, a pioneer work by Haruta et al. [5, 6] showed that gold nanoparticles (AuNPs) deposited on transition metal oxides (Fe, Co, Ni, Ti) can oxidize CO at a temperature as low as − 70 °C. These investigations have confirmed the outstanding properties of gold at nanoscale in heterogeneous catalysis. Carbon monoxide oxid
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